This invention relates generally to imaging systems and more particularly to systems and methods for using a crystallinity of a substance to identify the substance.
The events of Sep. 11, 2001 instigated an urgency for more effective and stringent screening of airport baggage. The urgency for security expanded from an inspection of carry-on bags for knives and guns to a complete inspection of checked bags for a range of hazards with particular emphasis upon concealed explosives. X-ray imaging is a widespread technology currently employed for screening. However, existing x-ray baggage scanners, including computed tomography (CT) systems, designed for detection of explosive and illegal substances are unable to discriminate between harmless materials in certain ranges of density and threat materials like plastic explosive.
A plurality of identification systems based on a plurality of x-ray diffraction (XRD) techniques provide an improved discrimination of materials compared to that provided by the x-ray baggage scanners. Whenever x-rays encounter a crystalline material, a plurality of regularly spaced atoms of the crystalline material diffract some of the x-rays to generate a diffraction pattern. The diffraction pattern is indicative of a crystal structure of the crystalline material, and various properties of the crystalline material can be analyzed based upon particular features of the pattern. The XRD identification systems measure a plurality of d-spacings between a plurality of lattice planes of micro-crystals in the crystalline material.
However, the XRD identification systems for explosives detection and baggage scanning help identify the d-spacings, which identify the crystalline material with a limited confidence. The identification of the crystalline material to with the limited confidence may result in a false alarm problem for some classes of substances. There are certain types of explosives in which an explosive component cannot be identified by the XRD identification systems and the lack of identification leads to a high false alarm rate.